1. Field of the Invention
This invention relates to an image blur preventing apparatus for preventing image blur caused by hand vibration or the like in a camera, an optical apparatus or the like.
2. Related Background Art
In cameras today, operations important to photographing, such as exposure determination and focusing, are all automated and even those unskilled in camera operation rarely fail to perform photography. Recently, a system for correcting hand vibration of a camera has been studied and the applicant has disclosed such a system in Japanese Laid-Open Patent Application No. 3-188430, etc.
In the correction of hand vibration, it has been necessary to perform a locking operation after completion of a hand vibration correction driving operation or upon cosumption of a power source as a counter-measure for preventing damage due to disturbance of the correction optical means when carrying the camera in an unlocked state, and for preventing photographing in an unlocked state except during a hand vibration correction driving operation.
A system for preventing hand vibration will be briefly described here. The hand vibration of a camera during photographing is a vibration of usually 1 Hz to 12 Hz as a frequency. The basic concept for enabling a photograph to be taken free of image blur, even if such hand vibration is caused at a point of time whereat the shutter is released, is that vibration of the camera due to the hand vibration is detected and a correction lens is displaced by an amount in conformity with the detected vibration.
Accordingly, to enable a photograph to be taken which will not make one sense image blur, even if vibration of the camera is caused, it becomes necessary to first detect the vibration of the camera accurately, and then correct any change in the optical axis caused by the vibration.
This detection of the vibration can be effected, in principle, by providing means for detecting angular acceleration, angular velocity, angular displacement or the like, and means for electrically or mechanically integrating the output signal of the vibration detecting means and outputting angular displacement. On the basis of this detected information, a correction optical device for making the photo-taking optical axis eccentric is driven, whereby image blur suppression is effected. An embodiment of a blur prevention system using the vibration detecting means will be described with reference to FIG. 29 of the accompanying drawings. FIG. 29 shows a system for suppressing image blur resulting from a vertical vibration component 81p and a lateral vibration component 81y of a camera vibration (arrow 81).
In FIG. 29, the reference numeral 82 designates a lens barrel, the reference characters 83p and 83y denote vibration detecting means for detecting camera vertical vibration and camera lateral vibration, respectively, and the directions of vibration detection thereof are indicated by 84p and 84y, respectively. The reference numeral 85 designates a correction optical apparatus (86p and 86y denote coils for giving thrust to correction optical means including optical apparatus 85, and 87p and 87y designate detection elements for detecting the position of the correction optical apparatus 85), and this correction optical apparatus 85 is provided with a position control loop, and is driven with the outputs of the vibration detecting means 83p and 83y as a target value, to provide image stabilization in the image plane 88.
FIG. 30 of the accompanying drawings is an exploded perspective view of a correction apparatus according to the prior art, and FIG. 31 of the accompanying drawings is a plan view from locking means side after completion of assembly. The vicinity of the locking means in this example will now be described. A permanent magnet 718 (lock magnet) is incorporated in a through-hole 71i formed in a ground plate 71 and is magnetically coupled to a second yoke 72. A coil 720 (lock coil) is adhesively secured to a lock ring 719, and there is a bearing 719b on the back of the ear portion 719a of the lock ring 719, and armature rubber 722 is extended over an armature pin 721, which in turn is extended through the bearing 719b, whereafter an armature spring 723 is extended over the armature pin 721, is fitted into an armature 724 and is fixed by caulking. Therefore, the armature 724 is slidable in the direction of arrow 725 relative to the lock ring 719 against the armature spring 723. The lock ring 719 is rotatably mounted on the ground plate 71 by a so-called bayonet coupling wherein cut-away portions 719c (three locations) formed in the outer diameter of the lock ring are pushed in accord with the inner diameter projected portions 71j (three locations) of the ground plate 71, whereafter the lock ring 719 is rotated to therebyeffect anti-slippage. However, In order to prevent the lock ring 719 from rotating and the cut-aways from becoming the same in phase as the projections again and coming off the projections, lock rubber 726 is forced into the ground plate and rotation is regulated so that the lock ring 719 can rotate only by the angle .theta. of a cut-away portion 719d regulated by the lock rubber. A permanent magnet 718 (lock magnet) is also mounted on a lock yoke 727 mode of a magnetic material and is threadably coupled to the lock yoke with holes 727a (two locations) fitted to the pin 71k of the ground plate 71 and by holes 727b (two locations) and 711. A conventional closed magnetic circuit is formed by the permanent magnet 718 on the ground plate 71 side, the permanent magnet 718 on the lock yoke 727 side, the second yoke 72 and the lock yoke 727. The lock rubber 726 is prevented from slipping off by the lock yoke 727 being threadably coupled.
In FIG. 31, the lock yoke 721 is not shown.
A lock spring 728 is extended between a hook 719e on the lock ring and a hook 71m on the ground plate 71 and biases the lock ring 719 in a clockwise direction.
An adsorption coil 730 is inserted in an adsorption yoke 729 and is threadably coupled to the ground plate 71 by a hole 729a. The terminal of the coil 720 and the terminal of the adsorption coil 730 are soldered to the trunk portion 716d of a flexible base plate 716 by means of lead wire or the like.
The operation of this lock means will now be described. A support frame 75 holding an optical member is provided with three radial projections 75f, and in the locked state, the tip ends of the projections 75f fit to the inner peripheral surface 719g of the lock ring 719. To bring about an unlocked state, an electric current is supplied to the lock coil 720 by a control circuit, not shown, through the flexible base plate 716 to thereby produce a torque for rotating the lock ring 719 about the optical axis because there is a coil in the closed magnetic circuit. Thereby the lock ring 719 is rotated in a counter-clockwise direction against the spring force of the lock spring 728.
When the lock ring 719 is rotated, the armature 724 bears against the adsorption yoke 729 to thereby shrink the armature spring 723 and equalize the positional relation between the adsorption coil and the armature 724 and thus, the lock ring stops its rotation. When at this time, the adsorption coil is electrically energized, the armature 724 is adsorbed by the adsorption yoke 729. Even if thereafter the coil 720 is deenergized, the lock ring can be maintained at this position.
At this time, the projections 75f of the support frame 75 are in respective positions opposed to three cams 719f provided in the inner diameter of the lock ring and therefore, the support frame becomes movable in the directions 713p and 713y by the clearance between the projections 75f of the support frame and the cams 719f.
To bring about a locked state, the electrical energization of the adsorption coil 730 is stopped, whereby the adsorbing force of the armature 724 becomes null and the lock ring 719 is rotated by the lock spring 728, and the locked state of FIG. 31 is brought about.
The other members shown in FIG. 30 will hereinafter be described.
Projected ears 71a on the back of the ground plate 71 (three locations, one of which is hidden and unseen) fit to a lens barrel not shown, and a conventional lens barrel roller or the like is screwed to a hole 71b and is fixed to the lens barrel.
The second yoke 72 which is a magnetic material and is luster-plated is screwed to the hole 71c of the ground plate 71 by a screw extending through a hole 72a. Also, a permanent magnet (shift magnet) such as a neodymium magnet is magnetically attracted to the second yoke 72.
The direction of magnetization of each permanent magnet 73 is the direction of arrow 73a, as indicated in FIG. 30.
Coils 76p and 76y (shift coils) are patching-secured to the support frame 75 to which a lens 74 is fixed by a C-ring or the like, and light projection elements 77p and 77y such as IREDs are adhesively secured to the back of the support frame 75, and emergent light enters position detecting elements 78p and 78y such as PSD's through slits 75ap and 75ay.
Support balls 79a, 79b having spherical tip ends such as POM's and a charge spring 710 are inserted in the holes 75b (three locations) of the support frame 75, and the support ball 79a is heat-caulked and fixed to the support frame 75 (the support ball 79b is slidable in the direction of extension of the holes 75b against the spring force of the charge spring 710).
Referring to FIG. 32A of the accompanying drawings which is a transverse cross-sectional view of the correction optical apparatus after assembled, the support ball 79b, the charged charge spring 710 and the support ball 79a in the named order are fitted into the hole 75b of the support frame 75 in the direction of arrow 79c (the support balls 79a and 79b are parts of the same shape) and finally, the peripheral end portion 75c of the hole 75b is heat-caulked to thereby effect the anti-slippage of the support ball 79a.
A cross-sectional view of the hole 75b in a direction orthogonal to FIG. 32A is shown in FIG. 32C of the accompanying drawings. Also, a plan view in which the cross-sectional view of FIG. 32C is seen from the direction of arrow 79c is shown in FIG. 32B, and the depths of ranges indicated by characters A to D in FIG. 32B are shown at A to D in FIG. 32C.
The rear end portion of the vane portion 79aa of the support ball 79a is received and regulated within the range of a surface of depth A and therefore, by the peripheral end portion 75c being heat-caulked, the support ball 79a is fixed to the support frame 75.
Since the fore end portion of the vane portion 79ba of the support ball 79b is received within the range of a surface of depth B, the support ball 79b does not slip out of the hole 75b in the direction of arrow 79c due to the charge spring force of the charge spring.
Of course, when the assembly of the correction optical apparatus is complete, the support ball 70b is received by the second yoke 72 and therefore, the support ball 70b does not slip out of the support frame, but rather a surface of slippage preventing range B is provided with the assembly property taken into account.
The shape of the hole 75b of the support frame 75 of FIGS. 31 and 32A to 32C does not require a complicated inner diameter slide mold even when the support frame 75 is molded, but can be molded by a simple two-division mold pulled in a direction opposite to the direction of arrow 79c. Therefore, dimensional accuracy can be accurately set correspondingly thereto.
Also, the support balls 79a and 79b are interchangeable parts and, therefore, there is no error of assembly and this is advantageous in terms of the maintenance of parts.
Turning back to FIG. 30, for example, grease of the fluorine origin is applied to the bearing portion 75d of the support 75 and an L-shaped shaft 711 (of a non-magnetic stainless material) is inserted thereinto, and the other end of the L-shaped shaft 711 is inserted into a bearing portion 71d (to which grease is likewise applied) formed on the ground plate 71, and the three support balls 79b are all placed on the second yoke 72 and the support frame 75 is contained in the ground plate 71.
Next, the positioning holes 712a (three locations) of the first yoke 712 are fitted to the pins 71f (FIG. 32C, three locations) of the ground plate 71, and the first yoke 712 is received by receiving surface 71e (five locations) and is magnetically coupled to the ground plate 71 (the magnetic force of the permanent magnet 73).
Thereby, the back of the first yoke 712 bears against the support ball 79a, and the support frame 75 is sandwiched between the first yoke 712 and the second yoke 72 and is positioned in the direction of the optical axis.
Grease of the fluorine origin is also applied to the surfaces of contact between the support balls 79a, 79b and the first yoke 712 and the second yoke 72, and the support frame 75 is freely slidable relative to the ground plate 71 in a plane orthogonal to the optical axis.
The L-shaped shaft 711 supports the support frame 75 for sliding movement only in the directions of arrows 713p and 713y relative to the ground plate 71, whereby the rotation (rolling) of the support frame 75 relative to the ground plate 71 about the optical axis is regulated.
The backlash of the fitting (play or tolerance) between the L-shaped shaft 711 and the bearing portions 71d, 75d is set large in the direction of the optical axis to thereby prevent them from fitting overlappingly with the regulation in the direction of the optical axis by the sandwiching between the support balls 79a, 79b and the first yoke 712 and the second yoke 72.
An insulating sheet 714 is put on the surface of the first yoke 712, and a hard substrate 715 having thereon a plurality of IC's (position detecting elements 78p, 78y, output amplifying IC, coils 76p, 76y, driving IC, etc.) is threadably coupled to the hole 71g of the ground plate 71 with a hole 715b and the hole 712b of the first yoke 712 with the positioning holes 715a (two locations) fitted over the pins 71h (two locations, FIG. 32C) of the ground plate 71.
The position detecting elements 78p and 78y are positioned by a tool and are soldered to the hard substrate 715, and a signal transmitting flexible substrate 716 has its surface 716a heat-pressed against the back of the hard substrate 715 within a range 715c encircled by a broken line.
A pair of arms 716bp and 716by extend from the flexible substrate 716 in the direction of a plane orthogonal to the optical axis, and are hooked on the hook portions 75ep and 75ey, respectively, of the support frame 75, and the terminals of IREDs 77p, 77y and the terminals of coils 76p and 76y are soldered thereto.
In this manner, driving of the IREDs 77p, 77y and the coils 76p, 76y is effected from the hard substrate 715 through the flexible substrate 716.
The arm portions 716bp and 716by of the flexible substrate 716 have bent portions 716cp and 716cy, respectively, and by the resiliency of these bent portions, the loads of the arm portions 716bp and 716by relative to the movement of the support frame 75 in a plane orthogonal to the optical axis are reduced.
The first yoke 712 has a protruded surface 712c, formed by embossing, and the protruded surface 712c passes through a hole 714a in the insulating sheet 714 and is arranged in direct contact with the hard substrate 715.
An earth (GND: ground) pattern is formed on that side of this contact surface which is adjacent to the hard substrate 715, and the hard substrate 715 is threadably coupled to the ground plate, whereby the first yoke 712 is grounded, thereby preventing the first yoke for becoming an antenna and transmitting noise to the hard substrate 715.
A mask 717 is positioned by the pin 71h of the ground plate 71 and is fixed onto the hard substrate 715 by a both-surface tape (two-sided adhesive tape.
In the above-described example of the prior art, the lock ring 719 is normally pulled in a direction toward the locking state by the lock spring 728 and therefore, when a hand vibration correcting operation is performed, it is necessary to hold the lock ring 719 in its unlocking state by the adsorption coil 30, and an electric current must continue to be supplied to the adsorption coil 30 during the hand vibration correcting operation and thus, power consumption has been great. Also, the locking means itself requires a lock spring, a lock coil, a plurality of lock magnets, an adsorption coil, an armature, etc., and this has led to the problem that the apparatus itself becomes: bulky.
Also, in many examples of the prior art (Japanese Laid-Open Patent Application No. 62-18875, Japanese Laid-Open Patent Application No. 7-98469, etc.), the correction optical apparatus has therein a locking member capable of mechanically fixing and locking the displacement of the correction lens, and when an image blur correcting operation is unnecessary (a state in which an interchangeable lens carrying an image blur correcting device therein has been removed from a camera body or a state in which an image blur operation switch has been opened), driving means controlled by control means such as a CPU moves the locking member and fixes and locks it so as to make the optical axis of the correction lens coincident with the optical axis of the other lens, thereby preventing any damage due to disturbance vibration (such as vibration applied during carrying) caused by a backlash of the correction lens and the wasteful power consumption by the correction optical apparatus.